1. Technical Field
Present invention relates to an inkjet recording apparatus for ejection an ink droplet from a nozzle, and to a drive method of the inkjet recording head.
2. Description of the Prior Art
An inkjet recording apparatus is commonly known which records an image by ejecting a minute ink droplet from a nozzle and landing the droplet on a recording medium.
In recent years, in order to record the high quality image, technologies for high density nozzles and smaller sized ink droplets having been developed. As a method for minifying the ink droplet diameter, commonly known is a so-called Pull-Push method where a pressure chamber connecting to a nozzle opening is firstly expanded and after that contracted. According to this method, since mass of the ink droplet can be made small, dot diameter in recording is said to be minified.
As an inkjet recording apparatus utilizing this Push-Pull method, the apparatus provided with a drive section is known which applies voltage V1 for t1 time period onto a piezoelectric element to expand the volume of the pressure chamber, next applies voltage V2 for t2 time period to contract the volume of the pressure chamber, and after that applies voltage V3 for t3 time period to expand the volume of the pressure chamber (see for example Japanese Registration Patent No. 4161631, hereinafter to be called Patent Document 1).
However in a case where the pressure chamber is driven with a contraction pulse such as the one described in the above mentioned Patent Document 1, a pressure wave vibration which is generated at the edge portion of the drive pulse cannot be effectively canceled, and residual vibration remains largely. Therefore, to execute high frequency drive in this state is difficult. Further, in the Patent Document 1, a second contraction pulse is lastly applied to cancel the residual vibration. By applying the second contraction pulse, the total waveform of the pulses becomes long, which leads to decrease of the drive frequency. Further, even in the case where t2+t3=AL (AL: half of the acoustic resonance period of the pressure chamber) is satisfied without applying the second contraction pulse, as described in the Patent Document 1, the residual vibration cannot be effectively canceled, which leads to greatly decreasing the drive stability. In order to obtain sufficient drive stability, it is necessary to wait for a sufficient time period until the residual vibration decays before the next drive, which results in the decrease of drive frequency.
In view of the above mentioned problems, an objective of the present invention is to provide inkjet recording apparatus and a drive method of the inkjet recording head, which enables stable and high speed ink ejection of smaller droplet without decreasing the drive frequency.